HIV-associated dementia complex (HADC) is characterized by profound cognitive impairment and variable pathological changes. While one mechanism of neurologic dysfunction is believed to be cell loss resulting from release of toxins from HIV-infected macrophages and microglia, clinical signs are often not correlated with the degree of neuronal loss. Moreover, since marked neurologic improvement occurs with antiretroviral therapy, functional abnormalities in neurons may be important in addition to cell death. In addition to macrophage infection, recent in situ PCR studies have demonstrated restricted infection in neurons and astrocytes. Our hypothesis is that alterations in neural cell functions, as well as cell death, result from productive HIV-1 infection of macrophages/microglia and restricted infection in astrocytes and neurons, and that both neuronal dysfunction and cell death contribute to neurologic dysfunction in HADC. To study functional responses of human neurons relevant to the pathogenesis of HADC, we have developed a unique human neuronal cell culture system and panel of assays for specialized neuronal cell functions which can be applied in mixed co-cultures of neurons, primary macrophages, and astrocytes. Our goal is to better understand the functional and toxic responses of neurons to HIV-1 infection in the brain and how these responses are modulated through glial elements. The First Award proposal builds upon my background in neurotransmitter metabolism, HIV virology, and development of this unique system for functional analysis of differentiated human neurons. First, we will identify alterations of neuronal functions that result from HIV-1 infection in macrophages, and determine how such infection may ultimately kill neurons. This involves a detailed analysis of neurotransmitter enzyme expression and high-affinity neurotransmitter uptake in neurons, utilizing our recently developed glial/neuronal culture system. Second, we will define the role(s) of astrocytes in modulating neuronal functions. To do this, we will analyze effects of viral gene expression within astrocytes on astrocytic and neuronal functions, utilizing viral vectors and co-cultivation with HIV-1 infected macrophages. Third, we will determine the functional consequences of direct HIV-1 infection of neurons. We will utilize chronically-infected clonal neuronal cell derivatives to analyze effects of infection on cell functions in differentiating neurons and their modulation through glial contact. Because neurological dysfunction may occur independently of cell death it is critical to examine neuronal cell functional responses to HIV-1 infection in the brain. It is our expectation that these studies will provide a foundation for, ultimately, the rational development of novel therapeutic approaches to preservation of neurological function in HADC.